RFR: 8377368: [REDO] Mixed jstack cannot find function in vDSO

[Yasumasa Suenaga]

On Fri, 6 Feb 2026 18:01:17 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> We fixed mixed jstack failure when the call stack has frame in vDSO like `gettimeofday()` in [JDK-8376269](https://bugs.openjdk.org/browse/JDK-8376269). But it has been backouted due to build error (see [JDK-8377365](https://bugs.openjdk.org/browse/JDK-8377365) for details).
>> 
>> JDK-8376269 uses `memfd_create` to copy vDSO from coredump to temporal memory, however it cannot be used on older glibc - some CI works on glibc 2.12, it does not have `memfd_create` unfortunately.
>> 
>> Thus this PR proposes to use `tmpfile()` and `fileno()` to copy vDSO, as alternatives of `memfd_create()`. It works, and passed all serviceability/sa tests on Linux AMD64.
>> 
>> Changes from JDK-8376269 is https://github.com/openjdk/jdk/commit/0c315303865efe60de54276bbcf2faf174fd1d9b .
>
> I'm seeing the following failure on linux-x64-debug:
> 
> 
> Opening core file, please wait...
> hsdb> ERROR: address conflict @ 0x7ffe43ff4000 (existing map size = 8192, size = 3701, flags = 5)
> ERROR: can't read shared object's segments
> ERROR: failed to read libraries
> 
> 
> The core file fails to attach as a result of this.

@plummercj What is the address 0x7ffe43ff4000? Looks like vDSO...

Did you run on same kernel both crasher and clhsdb? I want to know same vDSO is loaded both because the error seems to happen on following code:;


        if ((existing_map->memsz != page_size) &&
            (existing_map->fd != lib_fd) &&
            (ROUNDUP(existing_map->memsz, page_size) != ROUNDUP(lib_memsz, page_size))) {

          print_error("address conflict @ 0x%lx (existing map size = %ld, size = %ld, flags = %d)\n",
                        target_vaddr, existing_map->memsz, lib_php->p_memsz, lib_php->p_flags);
          goto err;
        }

-------------

PR Comment: https://git.openjdk.org/jdk/pull/29610#issuecomment-3863385675